The polymerization of vinyl chloride or vinylidene chloride is normally conducted in pressure vessels with water in the presence of dispersion, suspension or emulsifying agents and free radical forming catalysts. The suspending agents usually employed include partially hydrolyzed polyvinyl acetate, polyvinyl alcohol, cellulose ether, gelatin, methyl cellulose and derivatives thereof. Catalysts normally employed are organic peroxides such as lauryl peroxide, benzoyl peroxide, acetyl cyclohexyl sulfonyl peroxide, acyl peroxide, isopropyl peroxydicarbonate, di-secondarybutyl peroxydicarbonate and other well known free radical forming catalysts. The polymerization normally is conducted in the range of 30.degree. C. to 60.degree. C. but as is well known may be conducted at higher or lower temperatures, as 0.degree. to 100.degree. C.
In any event, during the aqueous polymerization of vinyl chloride or vinylidene chloride monomers (hereinafter referred to as vinyl halide monomers), polymer deposits form on the inner walls of vessels and build up even more rapidly at certain trouble spots in commercial size reactors, depending in part on the design of the reactor, but generally, relating to areas where suspension flow is interrupted or is decreased, in those areas where there are "dead spots" and areas where small particles may be separated from the suspension and grow during the polymerization process. These areas include, for example, annular cavities, around baffle supports, thermocouples, nozzles, and the like. Another potential source of problem is at the bottom of reactors where there often is an area not completely drained when the reactor is emptied and these areas are dead spots. Further, many polymerization reactors for vinyl halide polymers have a glass lining and over a period of time this glass lining becomes cracked, broken and the base metal is exposed. These areas are also sources for abnormal polymer build up.
When polymer build up begins in these type of locations the build up tends to grow with successive charges at an increasing rate unless the reactor is cleaned after each polymerization. Polymer build up also contributes to poor quality polymer since it often breaks off during the course of polymerization and becomes intermingled with the polymer being polymerized. It is well known, of course, that such build up also interferes with heat transfer and the like.
It is known to be a toxological hazard for workers to enter the reactors to hand clean these polymer build ups, and while mechanical equipment has been devised to remove the polymer, it obviously is still desirable to improve the polymerization conditions such that the amount of polymer is reduced for economic, quality and other reasons, and as a minimum, that any undesired polymer build up that is formed is more readily removed by such mechanical cleaning means.